It is a known practice in textile yarn winding and spinning operations to employ mechanical or optical sensing devices located in the path of the yarn strand to a yarn collection point or takeup station to detect a break of the yarn strand and provide signals to stop the yarn takeup drive motor. The yarn strand break may be repaired and the winding station drive motor restarted.
Such "end down" yarn detection and sensing means located in the yarn strand path to detect breakage necessarily requires optical, electrical, or mechanical sensors which employ related circuitry and signal means to indicate the break and/or stop the motor driving the yarn takeup device.
It also has been proposed in textile yarn strand winding apparatus to monitor the operating conditions of the individual drive motor of each yarn takeup station to sense change in motor conditions resulting from a yarn break and stop the drive motor when the yarn break occurs.
Great Britain Patent Application 2218-117-A, published Nov. 8, 1989 discloses a yarn break detection device for a textile unit having an electrical drive motor whereby the power consumption to the motor is measured and compared to a reference value. If the consumption falls rapidly below a set minimum value, a stop motion signal switches off the unit.
Brushless DC motors without permanent magnets have been proposed for driving the individual spindle assemblies of a textile yarn ring spinning frame. In such spindle assemblies, the rotor of the motor is mounted on the spindle shaft which supportably rotates a yarn collection member, such as a bobbin, during the spinning operation. A ring rail with ring and traveler reciprocates vertically along the support bobbin to wind the yarn package. The lower end of the spindle support shaft is supported for rotation in a bolster section which has an outer housing mounted in fixed position to a spindle assembly support rail of the spinning frame. The stator of the motor is disposed in surrounding relation to the reactor and is mounted in fixed position in a housing supportably attached in suitable manner to the bolster housing or support rail of the ring spinning frame.
Brushless DC motors without permanent magnets often are interchangeably referred to as switched reluctance (SR) or variable reluctance (VR) motors. Reference to a VR motor herein is intended to include both terminologies. A VR motor has two sets of salient poles, one set on the stator which has phase windings around the poles and another set on the rotor which has no windings. The stator phase windings are sequentially energized with current pulses to rotate the rotor which is connected to a shaft output. The stator phase windings are sequenced, or commutated, by signals from a rotor position sensor. The rotor position sensing means may comprises optical sensors or magnetic sensors of the Hall effect type. The sensors typically are mounted in a fixed position on the stator or motor housing adjacent the path of rotation of the rotor, and the sensed means are fixed for rotation with the rotor.
In a typical three-phase, VR motor, three Hall effect sensors may be located 120.degree. arcuately apart, centered about the rotor shaft, and are fixed directly to the stator or to some fixture which locates them according to some known relationship with respect to the stator. A magnetic ring with four North regions and four South regions alternating in 45.degree. radial arcs of the ring are attached to the rotor or rotor shaft and serve as sensed means so that when the rotor rotates, sensor output signals can be used to directly commutate, i.e., cut on and off, the current to each of the motor phase windings as they locate each and every pole alignment.
It is known to provide control systems for adjusting various parameters of motor operation of a VR motor, such as speed, torque, phase communication, phase advance, and efficiency of the motor. Certain of such systems employ analog or digital memory to store optimum control parameters relating to switching angles to demand speed and operating torque. Certain other control systems employ theoretical equations derived to predict optimum phase advance as a function of speed.